Electrically powered aerial vehicles and flight control methods

ABSTRACT

An aerial vehicle includes at least one wing, a plurality of thrust producing elements on the at least one wing, a plurality of electric motors equal to the number of thrust producing elements for individually driving each of the thrust producing elements, at least one battery for providing power to the motors, and a flight control system to control the operation of the vehicle. The aerial vehicle may include a fuselage configuration to facilitate takeoffs and landings in horizontal, vertical and transient orientations, redundant control and thrust elements to improve reliability and means of controlling the orientation stability of the vehicle in low power and multiple loss of propulsion system situations. Method of flying an aerial vehicle includes the variation of the rotational speed of the thrust producing elements to achieve active vehicle control.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority from U.S. ProvisionalApplication Ser. No. 61/710,216 filed Oct. 5, 2012 which is incorporatedherein by reference.

TECHNICAL FIELD

This invention relates to the field of aerial vehicles in general andthe field of electrically powered aerial vehicles and a flight controlmethods in particular.

BACKGROUND

Electrically powered aerial vehicles and in particular vertical takeoffand landing (VTOL) vehicles have helicopter type configurations or wingtype configurations in which the engines must articulate (either ontheir own or with rotatable wings) for vertical and horizontaltranslational flight. Such vehicles are complicated.

SUMMARY

According to one aspect of the present invention there is provided anaerial vehicle including a cockpit located on a central longitudinalaxis of the vehicle, a fixed, elongated rectilinear wing spaced apartfrom each end of the cockpit and extending perpendicular to the centrallongitudinal axis, struts connecting the ends of the wings to thecockpit and to each other, a plurality of propellers on a leading edgeof each wing, the propellers having rotational axis such that the washfrom the propellers is directed along the surfaces of the wing toprovide lift and forward thrust to the vehicle, a plurality of electricmotors for driving the propellers, at least one battery for providingpower to the motors, and a flight control system having a separate motorcontroller for each motor to control the rotational speed of eachpropeller. According to another aspect of the present invention there isprovided an aerial vehicle including a fuselage located on a centrallongitudinal axis of the vehicle, an elongated rectilinear wingextending perpendicular to the central longitudinal axis and fixed toeach end of the fuselage, a plurality of propellers on a leading edge ofeach wing, the propellers having rotational axis such that the wash fromthe propellers is directed along at least one surface of the wing toprovide lift and forward thrust to the vehicle, a plurality of electricmotors for driving the propellers, at least one battery for providingpower to the motors, and a flight control system having a separate motorcontroller for each motor to control the rotational speed of eachpropeller.

According to a further aspect of the present invention, there isprovided a method of flying an aerial vehicle including a cockpit, upperand lower wings attached to the cockpit and a plurality of propellers oneach wing, the steps including increasing or decreasing the rotationalspeed of propellers on one wing relative the rotational speed ofpropellers on the other wing whereby the orientation of the vehiclerelative to the pitch axis can be varied.

According to a still further aspect of the present invention, there isprovided a method of flying an aerial vehicle including a fuselage,first and second wings attached to the fuselage and a plurality ofpropellers on each wing, the steps including increasing or decreasingthe rotational speed of propellers on one wing relative to therotational speed of propellers on the other wing whereby the orientationof the vehicle relative to the pitch axis can be varied.

According to a still further aspect of the present invention, one ormore of the propellers are sized and configured for a first speed orcondition, such as hover, while one or more other propellers areoptimized for one or more other speeds, such as, for horizontal flight.For example, in an eight propeller configuration, four propellers can beoptimized for hover flight in terms of one or more of the pitch,diameter, foil design and number of blades while four additionalpropellers can be optimized for forward flight, again in terms of one ormore of the pitch, diameter, foil design and number of blades. Incertain other aspects, one or more of the pitch, diameter, foil designand number of blades of one or more of the propellers may be varied toadapt the propellers for one or more other desired performancecharacteristic.

According to a further aspect of the present invention, there isprovided a method of flying an aerial vehicle including a cockpit, upperand lower wings staggered vertically and longitudinally relative to eachother and a plurality of propellers on each wing, the steps includingincreasing or decreasing the rotational speed of propellers on one wingrelative the rotational speed of propellers on the other wing wherebythe orientation of the vehicle relative to the pitch axis can be varied.

According to a still further aspect of the present invention, there isprovided an active control system for control of an aerial vehicle witha plurality of thrust producing elements of eight or more wherein thethrust producing elements are grouped into logical and physicalquadrants comprising of two or more thrust producing elements each. Thecontrol system allows for the control of the thrust producing elementsin the event of failure of all propulsion systems in the same quadrantby allowing some of the thrust producing elements in the oppositequadrant to produce negative thrust. This method allows for all thrustproducing elements, other than the elements operating in reverse, tooperate in a range allowing for controllability.

According to a still further aspect of the present invention, there isprovided an aerial vehicle including one or more wings, three or morethrust producing elements mounted in a fixed non-articulatingrelationship to the one or more wings, a plurality of electric motorsfor driving the thrust producing elements, at least one battery forproviding power to the motors, and a flight control system having amotor controller for controlling the rotational speed and direction ofrotation of each thrust producing element.

In certain embodiments, the vehicle may further include a fuselagelocated on a central longitudinal axis of the vehicle, wherein the oneor more wings comprising two wings extending perpendicular to thecentral longitudinal axis, the wings are stacked and spaced from eachother along the central longitudinal axis and along an axisperpendicular to the central longitudinal axis.

In certain embodiments, the vehicle may further include a bottom havinga first facet at a first angle and a second facet at a second angle,whereby the vehicle rests at a first orientation when resting on thefirst facet and rests at a second orientation when the vehicle rests onthe second facet, wherein the first orientation may be conducive to avertical or near vertical take-off and the second orientation may beconducive to a horizontal or near horizontal take-off.

In certain embodiments, the aerial vehicle is tailless, and the controlsystem is adapted vary the amount of rotational energy absorbed byindividual motors when the individual motors are operated in a generatormode and are driven by rotation of the thrust producing elementsconnected to the individual motors, thereby effecting control of theorientation of the vehicle without the use of control surfaces.

In certain embodiments, the number of thrust producing elements is atleast eight, the thrust producing elements are grouped into fourquadrants with at least two thrust producing elements located in eachquadrant, the control system is adapted to reverse the rotation of afirst thrust control element in a first quadrant, vary the rotation of asecond thrust control element in the first quadrant, when all thrustcontrol elements are not operating in a quadrant opposite the firstquadrant, thereby effecting control of the orientation of the vehicle.

In certain embodiments, one or more of the thrust producing elements areadapted for hover and one or more of the thrust producing elements areadapted for forward flight.

In certain embodiments, the vehicle further includes a battery energylevel monitor for determining the energy level in the battery configuredto take a first measurement of the voltage in the battery at an initialepoch under a substantially no-load condition, relate the voltagemeasurement to a value of potential energy stored in the battery at theinitial epoch, take a second measurement of voltage in the battery and ameasurement of current flow into or out of the battery at a subsequentepoch, integrate the second measurement of voltage and the current flowmeasurement with respect to time, determine an energy change from theintegration, and relate the energy change to the initial energy level tocalculate the energy level of the battery at the subsequent epoch.

In certain embodiments, the aerial vehicle in horizontal or nearhorizontal flight, the control system is adapted to increase rotation ofsome of the thrust producing elements to make a yaw turn whereby thevehicle turns substantially around the yaw axis but does not turnsubstantially around the pitch or roll axis.

According to a still further aspect of the present invention, there isprovided a method of operating an aerial vehicle comprising one or morewings, three or more thrust producing elements mounted in a fixednon-articulating relationship to the one or more wings, and a pluralityof electric motors for driving the thrust producing elements, includingdifferentially varying the thrust of the thrust producing elementsthereby altering the orientation of the vehicle.

In certain embodiments, the method further includes differentiallyvarying the amount of rotational energy absorbed by the individualmotors when the individual motors are operated in a generator mode andare driven by rotation of the thrust producing elements connected to theindividual motors, thereby effecting control of the orientation of thevehicle without the use of control surfaces.

In certain embodiments, the number of thrust producing elements is atleast eight and the thrust producing elements are grouped into fourquadrants with at least two thrust producing elements located in eachquadrant, and the method further includes reversing the rotationaldirection of a first thrust control element in a first quadrant, varyingthe rotational speed of a second thrust control element in the firstquadrant, when all thrust control elements are not operating in aquadrant opposite the first quadrant, thereby effecting control of theorientation of the vehicle.

In certain embodiments, the method further includes providing a batteryfor providing power to the motors, monitoring the energy level in thebattery including taking a first measurement of the voltage in thebattery at an initial epoch under a substantially no-load condition,relating the voltage measurement to a value of potential energy storedin the battery at the initial epoch, taking a second measurement ofvoltage in the battery and a measurement of current flow into or out ofthe battery at a subsequent epoch, integrating the second measurement ofvoltage and the current flow measurement with respect to time,determining an energy change from the integration, and relating theenergy change to the initial energy level to calculate the energy levelof the battery at the subsequent epoch.

In certain embodiments, the method further includes increasing therotational speed of some of the thrust producing elements to yaw thevehicle thereby inducing the vehicle to roll.

DRAWINGS

The invention is described below in greater detail with reference to theaccompanying drawings which illustrate preferred embodiments of theinvention, and wherein:

FIG. 1 is a perspective view of an aerial vehicle according to anembodiment of the present invention;

FIG. 2 is a bottom view of the vehicle of FIG. 1;

FIG. 3 is an isometric view of an aerial vehicle according to anotherembodiment of the present invention;

FIG. 4 is a top view of the vehicle of FIG. 3;

FIG. 5 is a bottom view of the vehicle of FIGS. 3 and 4;

FIG. 6 is an electrical schematic of a flight control system usable inthe vehicles of FIGS. 1 to 5;

FIG. 7 is an electrical schematic of an alternate flight control systemusable in the vehicles of FIGS. 1 to 5; and,

FIG. 8 is an electrical schematic of an alternate flight control systemusable in the vehicles of FIGS. 1 to 5.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2 of the drawings, one embodiment of the aerialvehicle of the present invention includes a cockpit indicated generallyat 1 for accommodating an operator 2. Wings 3 and 4 are spaced apartfrom the front and rear of the cockpit 1. The wings 3 and 4 areperpendicular to the central longitudinal axis of the vehicle. A firstpair of outer struts 5 extend between the wings 3 and 4 on each side ofthe cockpit 1. The outer struts 5 are connected to the wings 3 and 4proximate their outer ends. The struts 5 are also connected to thecenters of the sides of the cockpit 1.

The sides of the cockpit 1 are defined by inner struts 7, which define adiamond shaped structure extending between the centers of the wings 3and 4. The cockpit 1 is basically a backrest 8 and a floor 9 (FIG. 2)extending between the struts 7. The struts 5 are connected to the innerstruts 7 and thus to the cockpit at the longitudinal center of thevehicle. The struts 5 and 7 are connected to the wings 3 and 4 by barrelhinges (not shown), which include removable pivot pins. Of course, thestruts can be permanently connected to the wings 3 and 4. By the sametoken, the cockpit 1 can separate from and permanently connected to thestruts 5 and 7 or removable for disassembly of the vehicle fortransporting it in pieces. In other embodiments, a fuselage may beprovided. In further embodiments, the vehicle may have more than twowings, for example three wings, and motors may be provided on more thantwo wings.

Each of the elongated, rectilinear wings 3 and 4 includes an inner boxor frame (not shown) formed of a rigid foam such as Styrofoam® coveredby a layer of epoxy-carbon composite. The box contains four electricbatteries 13 (FIG. 6) for providing energy to a like number of DCelectric motors 14. In other embodiments, the wings 3 and 4 may be ofdifferent construction and the electric batteries may be housedelsewhere in the vehicle.

The motors 14 are electronically commutated motors, and preferableoutrunner brushless DC motors. The motors 14 may be air cooled using avacuum disc (not shown) for evacuating air from the motors and in turndrawing air into the motors 14 preferably from the back of the motors.The vacuum discs are driven by the motors 14 and help cool the motors 14especially when air is not flowing to the motors 14 when the vehicle isstationary, such as when the vehicle is on the ground or hovering. Themotors 14 also include flux rings (not shown) defined by steel ringswith super magnets spaced around the inner circumferences of the steelrings and stators inside the rings. In one embodiment of the presentinvention, the flux rings are formed using cylindrical laminated steelsections, preferably concentric layers of electronic steel bondedtogether with structural epoxy. The flux ring structure of the rotor ofthe motor 14 is optional. In certain embodiments, a conventional solidrotor ring may be used. The preferred motors are capable ofapproximately 20 peak horsepower for about 2 minutes. The batteries arepreferably lithium polymer batteries but other suitable batteries may beused. An on-board battery charger (not shown) receives power from astandard household 110 volt outlet. In other embodiments, other types ofelectrically powered motors may be used. For example, motors of othersuitable power and speed capacities and types (such as but not limitedto inrunner brushless DC motors), may be used.

The motors 14 are mounted on the top, leading edge 15 of each wing 3 and4 for driving four propellers 16. The motors 14 are oriented on thewings 3 and 4 such that the plane defined by the rotation of eachpropeller 16 is preferably inclined by 6° with respect to a centrallongitudinal plane of the wing to which they are attached such that thepropellers 16 are orthogonal to the direction of flight of the vehiclewhen the vehicle is in horizontal flight. However, the angle ofinclination of the plane of the propellers may vary in other embodimentsdepending upon the optimum characteristic of the vehicle, such as forbut not limited to speed, load and angle of attack. For example, theangle of inclination may be as small as 0°, may a negative angle, or maybe 3° for higher speed applications, or greater than the preferred 6°.In other embodiments, the inclination of the propellers on one wing maydiffer from the inclination of the propellers on the other wing. Incertain embodiments, the propellers need not all have the same pitchangle. For example, when eight propellers are used, a first set of fourpropellers may have a certain forward pitch for high speed travel and asecond set of four propellers may have a shallower pitch, relative tothe forward pitch of the first set of four propellers, for hover. Inother embodiments, the diameter of the propellers may vary. For example,smaller propellers may be selected for improved hover control. Othercombinations of pitch, diameter, foil design and number of blades may beused according to the operational needs of the vehicle.

While each wing 3 and 4 is provided with four propellers 16, it will beappreciated that two, six, eight or more than eight propellers could beprovided on each wing. Certain propellers rotated in one direction asindicated by the arrows A in FIG. 1 and all of the remaining propellersrotated in the opposite direction as indicate by arrows B in FIG. 1. Thedirection of rotation of each propeller may vary in other embodiments.

The aerial vehicle of FIGS. 3 to 5 is similar to the vehicle of FIGS. 1and 2 except that the cockpit 1 is part of a fuselage 20 extendingbetween the centers of the front and rear wings 3 and 4 respectively.The fuselage 20 includes struts 5 (FIG. 3) and a skin covering thestruts and a frame (not shown) behind the seat back 8. The cockpit 1 iscovered by a domed canopy 21, and the bottom 22 of the fuselage 20 ismulti-faceted. The bottom 22 includes a first bottom surface 47 at afirst angle, a second bottom surface 48 at a second angle and a thirdbottom surface 49 at a third angle. This permits the vehicle when on theground to site at three angles of repose. In certain embodiments, thevehicle may sit on bottom surface 47 at a first angle of repose or onbottom surface 48 at a second angle of repose or on bottom surface 49 ata third angle of repose. In certain embodiments, the surface on which tosit the vehicle may be chosen for example to facilitate take-off. Forexample, for a near horizontal take-off orientation, the vehicle may siton the bottom surface 47. For a near vertical take-off orientation, thevehicle may sit on the bottom surface 49. It is understood that thebottom 22 is not limited to three bottom surfaces or to the anglesdepicted in FIG. 3. In certain embodiments, the bottom 22 may in wholeor in part be curved or arcuate as opposed to multi-facetted. In certainother embodiments, the fuselage may not include struts or a canopy andthe fuselage may be smooth or curved instead of multi-faceted.

Referring to FIG. 6, the operation of the aerial vehicle is controlledby a flight control system, which includes a motor controller 24connecting each motor 14 to a battery 13. In FIG. 6, to facilitate anunderstanding of the control system, the motors 14 rotating in thedirection of arrows A (FIG. 1) are labeled A1-A4, motors A1-A2 being onone wing 4 and motors A3-A4 being mounted on the other wing 3, andmotors 14 rotating in the direction of arrows B are labeled B1-B4,motors B1-B2 being mounted on wing 4 and motors B3-B4 being mounted onwing 3. The batteries 13 and motor controllers 24 connected to themotors A2-A4 and B1-B4 are also labeled A1-A4 and B1-B4, respectively.The batteries 13 are in turn connected to three power supply type “OR”gates 25. A separate back-up battery 26 is connected to the “OR” gates25 for providing emergency power in the event that the batteries 13become sufficiently discharged that they can no longer operate themotors 14. Each “OR” gate 25 is connected to a flight processor 17,which is connected to a sensor package 28 for measuring one or more ofthe vehicle's velocity, orientation and acceleration.—Each sensorpackage preferably includes three solid state gyroscopes (not shown) formeasuring rotational acceleration—in three orientations, threeaccelerometers (not shown) for measuring acceleration in threeorientations, a magnetometer (not shown) for measuring magnetic fieldstrength in three orientations, a barometric pressure sensor (not shown)and a GPS device (not shown). It will be appreciated that more or fewersensor packages, more or fewer sensors per sensor package and fightprocessors can be used. However, it is preferred and advisable to haveredundant controls in the vehicle. The flight processors 27 take inputfrom the sensor packages 28 and using software running on each flightprocessor 27, each flight processor 27 acts as a virtual inertialmeasuring unit (“Virtual IMU”) (not shown) and calculates vectors for apoint on the aerial vehicle representing the centre of gravity. Thevectors calculated include a position vector, an orientation vector, avelocity vector and an acceleration vector. These vectors can becalculated for points on the aerial vehicle other than the centre ofgravity. Not all of the vectors need to be calculated, or not each time.

The flight processors 27 also provide data to a tablet computer 29 whichacts as a display for the user 2. A different type of display may beused or omitted altogether. The GPS device is used to correct theVirtual IMU in accelerated frames of reference. The GPS device isoptional.

Each flight processor 27 is also connected to a joystick 31 and athrottle stick 32 both of which are controlled by the operator 2 of thevehicle. A cellular network data link 33 and/or a WiFi data link 34 canbe connected to the computer 29.

In operation, each processor 27 receives data from each sensor package28 and uses a polling method to average out the sensor information andcalculate the Virtual IMU which preferably is calculated at the centerof gravity of the vehicle to calculate the orientation and altitude ofthe vehicle. The polled data is used by each processor to adjust therotational speed of the propellers by sending the appropriate commandsto the motor controllers. The motor controllers receive data from eachof the processors 27 and use polling to determine which data to use incontrolling the motors 14. The control system is adapted to providethrust vector redundancy such that a loss of a motor will not result in“loss of control”.

In certain embodiments, a suitable conventional IMU may be used whereinsensor data is processed in a conventional manner and not at a virtualpoint on the aerial vehicle.

In certain embodiments, it is not essential to use a polling method.Other conventional methods, implemented as programmed algorithms, toanalyze the sensor information may be used. For example, in place ofpolling, outlier sensor information can be rejected and the remainingsensor information averaged.

On a full charge, the batteries 13 provide approximately 5 kilowatthours of electrical energy. The lithium polymer batteries 13 must not berun down below a threshold electrical energy level, such as 5%. If theyare depleted below that level, the battery is usually damaged. Thethreshold energy level can, however, be used as a one time battery powerreserve. Should the energy level of one or more batteries fall below thethreshold energy level, the remaining energy can be used on a one-timebasis to continue to provide power to the motors 14 to enable theoperator 2 to make an emergency landing. The operating range of theindividual cells of the batteries is about 3.6 volts per cell (theminimum threshold electrical level where the battery is considered to be“empty”) to 4.2 volts (where the battery is considered to be full). Allof the batteries 13 are connected to a common bus and are thusinterconnected. This provides for balancing of any asymmetricallyloading of the motors 14 and also permits the motors 14 to draw energyfrom any of the batteries 13. No single low battery will be the limitingfactor in the flight. The electrical connections between the batteries13 and the motors 14 are preferably minimized to minimize resistanceloses. Isolators 40 (groups of three isolators are identified by asingle reference numeral 40) are provided to isolate certain componentsin the control system from power surges and the like

Upon starting up the control system but without starting the motors 14,the voltage and temperature in each cell or set of cells of the battery,without the load of the motors, are measured. The battery voltages andtemperatures are then used to derive the amount of stored energy in eachbattery by for example using a concordance table which relates batteryvoltage and temperature to stored energy level. The initial start-upenergy of the cells of the batteries are recorded. Thereafter, for theduration of the flying session, the power flow in and out of eachbattery is measured. The power flow values are used to interpolatechanges (as a result of depletion or charging) in stored energy for eachof the batteries. The stored energy levels may be displayed to theoperator in the form of a battery power level display.

In certain embodiments, the energy content of individual battery cellsof the on-board energy storage system is measured by measuring thevoltage under a static or no load condition, along with the temperature.A battery typically has a plurality of battery cells. With the measuredstatic voltage and temperature the energy content at the measuring epochcan be calculated or determined from a look-up table. Changes in theenergy content of the cells may be calculated by measuring the powerflowing in (for example from charging) and out (for example fromapplying a load such as running the motors) of the battery cells.

In certain embodiments, the energy in each battery 13 is continuouslydetermined by calculating the initial battery energy and thenintegrating the measured power over time. Initial battery energy isdetermined by measuring both voltage and temperature of each batterycell under substantially no-load conditions. A trivial load such as theload to run a multi-meter may be applied to the battery duringmeasurement and still maintain a substantially no-load condition. Whileit is not essential to measure the temperature, measurement accuracy maybe significantly affected depending upon the temperature and themeasurement tolerances required. If the temperature is not measured,only the voltage measurement is related to stored energy level using atable of concordance or the like. The concordance between voltage and,voltage and temperature, to stored energy level for a battery cell maybe determined, for example, through routine testing of a battery cell.The battery energy monitoring may be incorporated into the controlsystem.

Referring to FIG. 7, in another embodiment of the present invention, thecontrol system is identical to that described herein with respect toFIG. 6 except that three back-up batteries 42 are provided instead ofjust one. Each back-up battery 42 is connected to an OR gate 25.

Referring to FIG. 8, in another embodiment of the present invention, thecontrol system is identical to that described herein with respect toFIG. 7 except that a back-up joystick 44 and a back-up throttle 46 areprovided with the associated wiring changes to accommodate them. Eachflight processor 27 is also connected to back-up joystick 44 and back-upthrottle stick 46 both of which are controlled by the operator 2 of thevehicle. The back-up joystick 44 provides identical functionality tojoystick 31, and back-up throttle 46 provides identical functionality tothrottle 32 are designed to provide redundant control functionality inthe event of a failure of joystick 31 and/or throttle 32. In certainembodiments, the joystick 44 can provide lesser functionality to thejoystick 31.

A regenerative braking/low power stability system is also provided. In afull power out situation, the propellers will “windmill” under controlof a flight controller, allowing the vehicle to glide rather than tolose all dynamic stability as most multi-rotor, artificially stabilizedaircraft would. The rotation of the propellers 16 can be used to chargethe batteries 13 such that, if a sufficient charge is built up duringthe descent, the motors 14 may be restarted long enough to enable acontrolled landing. In a full or partial power out situation, the glideand/or orientation of the vehicle can be controlled by controlling therotational speed of the “windmilling” propellers. This is accomplishedby increasing or decreasing the drag on the spinning propellers 16 byremoving varying degrees of rotational energy. In this manner,aero-braking may be used to actively control orientation and glide angleof the vehicle in a full or partial power-out situation. For example,one or more motors may still be operating.

The regenerative braking system is optional. Varying the rotationalspeed of the motors, operating in an electrical generator mode, can beused to control the amount of power each motor is absorbing from thepropeller and to use that power to charge the battery system, controlthe orientation and/or glide angle and/or speed of the vehicle. Incertain embodiments, energy may be removed from the motors throughresistive heating and the heat dissipated. In certain other embodiments,energy may be removed from the motors by using the electrical energygenerated by the motor in generator mode to charge an on-board battery.In certain other embodiments, internal resistance of the motor may beused. For example, electrical switching may be used to alter theinternal resistance of the motor. In certain other embodiments,mechanical breaking may be used to control the rotational speed of themotor. In certain embodiments, a combination of one or more of theforegoing energy absorbing methods and systems may be used. In certainembodiments, the control system is adapted to carry out control throughregenerative braking.

The aerial vehicle is equipped with an optional ballistic parachute (notshown). The parachute is housed in a compartment located in the cockpit.The parachute is designed to be deployed in an emergency situation suchas a power out situation.

In certain embodiments, the vehicle has an empty weight of approximately250 lbs and a useful load of approximately 450 lbs. The gross take-offweight is approximately 700. The vehicle has a cruising speed ofapproximately 55 mph and a range (with reserve) of approximately 30miles. The vehicle's hover power is approximately 50% of maximum power,hover power in ground effect is approximately 30% of maximum power andcruise power is approximately 10% of maximum power. The vehicle is notlimited to such specifications.

As shown in FIGS. 1 and 3, when at rest, the vehicle preferably sits onthe ground with the wings inclined at approximately 45° with respect tothe ground. While an inclination of approximately 45° is preferred, thewings may be inclined with respect to the ground at an angle rangingfrom approximately 90° for fully vertical take off to approximately 0°for horizontal take-off. In alternative embodiments, the wings 3 and 4are not parallel. The wing 3 for example may have a steeper “angle ofattack” than the wing 4 to for example stall the wing 3 before the wing4 such as in a power out glide situation. In other embodiments, the wing3 may be designed with wing geometries (e.g. size, profile andorientation) that make the wing 3 conducive to gliding in a power outsituation.

To take off, the tablet computer 29 is booted and the control systemactivated. Using the throttle stick 32, the motors 14 are turned on andthe power increased to the point where the vehicle lifts from the groundin an approximately 45° degree trajectory with respect to the ground.Power to the motors 14 is adjusted as needed. The vehicle can continueto be flown in such a trajectory. To vary the inclination of thetrajectory, such as to pitch the upper wing forward, the rotationalspeed of some or all of the propellers 16 on the upper wing 4 isincreased relative to the propellers on the lower front wing 3 or therotation of some or all of the lower wing propellers is decreasedrelative to the upper wing propellers or a combination thereof. Thispitch control method also applies when the vehicle is in a vertical or anear vertical orientation, including for vertical or near vertical takeoff. This pitch control method may be used to decrease the angle ofattack of the wings to transition to horizontal or near horizontalflight or to increase the angle of attack of the wings to move tovertical or near vertical flight. Take off can also occur in a slightreverse direction or a sideways direction.

To land, power may be adjusted such that the vehicle descends at adownward trajectory of approximately 45° with respect to the vertical.In other embodiments, the angle of attack of the wings can be increasedto transition the vehicle from horizontal or near horizontal flight to avertical or near vertical orientation and the vehicle may then descendto the ground by reducing power to the motors as needed.

In order to bank the vehicle in horizontal or relatively horizontalflight, the rotational speed of some of the propellers 16 is increasedrelative to the rotational speed of other propellers 16. In anembodiment where the propellers 16 driven by motors A1, A2, A3, A4rotate in the same direction (such as indicated by arrows A), and thepropellers driven by motors B1, B2, B3, B4 rotate in a counter direction(such as indicated by arrows B), the vehicle, may be banked byincreasing the rotational speed of the propellers 16 driven by motorsA1, A2, A3, A4 relative to the rotational speed of the propellers 16driven by motors B1, B2, B3, B4. This may be accomplished by increasingthe rotational speed of the motors A1, A2, A3, A4 and decreasing therotational speed of the motors B1, B2, B3, B4, increasing the rotationalspeed of the motors A1, A2, A3, A4 while maintaining the rotationalspeed of the motors B1, B2, B3, B4, or maintaining the rotational speedof the motors A1, A2, A3, A4 while decreasing the rotational speed ofthe motors B1, B2, B3, B4. It will be appreciated that in otherembodiments, other propeller rotation configurations can be similarlycontrolled.

In certain embodiments of the present invention, in order to conduct aturn of the vehicle around the yaw axis in horizontal flight or nearhorizontal flight, the rotational speed of the propellers 16 driven bymotors A1, A2, B3 and B4 is increased or decreased relative to thepropellers 16 driven by motors A3, A4, B1 and B2 in a manner analogousto that described herein with respect to banking. In certainembodiments, superposed modulation of motors A1, A2, A3 and A4 relativeto motors B1, B2, B3 and B4 may be used to control the bank angle of thevehicle for a turn coordinated about the yaw and roll axes.

In certain embodiments of the present invention, the rotational speed ofthe propellers 16 on one side of the vehicle can be increased relativeto the propellers on the other side to make a decoupled yaw turn whilethe vehicle is in horizontal or near horizontal flight such that thevehicle turns around the yaw axis but does not turn substantially aroundthe pitch or roll axis. This is also sometimes referred to as a“skidding” turn in conventional aviation. The turn may be controlled byincreasing the rotation of propellers driven by motors A1, A2, B3 and B4relative to the speed of propellers driven by motors A3, A4, B1 and B2while conducting superposed modulation of motors A1, A2, A3 and A4relative to B1, B2, B3 and B4 motors in order to stabilize the vehicleabout the roll axis. This will cause the vehicle to conduct a turn ofthe vehicle about the yaw axis while the vehicle does not turnsubstantially around the roll or pitch axes.

The propellers 16 are arranged in pairs in four quadrants relative tothe centre of the vehicle. If one motor 14 fails during operation of thevehicle, power to the other motor 14 in the same quadrant can beincreased to increase the rotational speed of the propeller 16 tocompensate for the failure. For example, if motor A1 fails, power tomotor A2 can be increased to compensate for the failure. The samecompensation method may be applied to motors arranged in otherconfigurations provided that the configuration is relativelysymmetrical.

In the event of a failure of two motors 14 in the same quadrant duringoperation, a motor 14 in the opposite quadrant is reversed and the othermotor 14 in that quadrant is modulated. For example, if motors A3 and A4fail, motor A1 can be reversed and motor A2 modulated or alternatively,motor A2 can be reversed and motor A1 modulated.

It should be noted that the figures merely depict certain possibleconfigurations of aerial vehicles that utilize the propulsion andcontrol systems described herein, and that fewer or more motors 14 maybe used without deviating from the spirit of the invention. Furthermore,the cockpit 1, fuselage 20 and struts are non-essential. Fewer or morewings can be used but there must be at least one wing or airfoil.Various wing structures and sizes can be used including a complete ringwing structure, as can other foil sections such as tapered and twisted.The propulsion and control systems according the present invention maybe used as appropriate with such wings or foils. A flying wing structurecan be employed such as a complete ring wing structure.

In certain embodiments of the present invention, the vehicle does notinclude a tail or rudder and can be substantially controlled bydifferential thrust, that is varying the thrust of one or more of thethrust producing elements. In certain other embodiments of the presentinvention, the vehicle does not include any control surfaces and can besubstantially controlled by differential thrust. In certain otherembodiments of the present invention, the vehicle does not include anycontrol surfaces except for one or more trim tabs, and can besubstantially controlled by differential thrust.

Aerial vehicles according to embodiments of the present invention arenot limited to the control systems described herein. It will beappreciated that the control systems described herein are exemplary ofcontrol systems that may be used to control the vehicle. It will beappreciated that other suitable control systems, including syntheticcontrol systems, may be used to carry out the desired control of aerialvehicles according to embodiments of the present invention.

The propulsion system for vehicles according to embodiments of thepresent invention are not limited to propellers. In certain embodiments,other thrust producing elements may be used such as turbines and ductedfans. Various combinations of different thrust producing elements mayalso be used.

Aerial vehicles according to embodiments of the present invention may bemanned or unmanned. Aerial vehicles according to embodiments of thepresent invention may be controlled by a human operator in the vehicleor remotely or a combination thereof.

I claim:
 1. An aerial vehicle comprising: one or more wings, three ormore thrust producing elements mounted in a fixed non-articulatingrelationship to the one or more wings, a plurality of electric motorsfor driving the thrust producing elements, at least one battery forproviding power to the motors, and a flight control system having amotor controller for controlling the rotational speed and direction ofrotation of each thrust producing element.
 2. The aerial vehicleaccording to claim 1, further comprising: a fuselage located on acentral longitudinal axis of the vehicle, wherein the one or more wingscomprising two wings extending perpendicular to the central longitudinalaxis, wherein the wings are stacked, and wherein the wings are spacedfrom each other along the central longitudinal axis.
 3. The aerialvehicle according to claim 2 wherein the vehicle further comprises abottom having a first facet at a first angle and a second facet at asecond angle, whereby the vehicle rests at a first orientation whenresting on the first facet and rests at a second orientation when thevehicle rests on the second facet.
 4. The aerial vehicle according toclaim 3 wherein the first orientation is conducive to a vertical or nearvertical take-off and the second orientation is conducive to ahorizontal or near horizontal take-off.
 5. The aerial vehicle accordingto claim 1, wherein the number of thrust producing elements is selectedfrom the group consisting of 3, 4, 6, 8, 10 and
 12. 6. The aerialvehicle according to claim 1, wherein the thrust producing elements areselected from the group consisting of propellers, turbines and ductedfans.
 7. The aerial vehicle according to claim 1, wherein the vehicle istailless, and the control system is adapted vary the amount ofrotational energy absorbed by individual motors when the individualmotors are operated in a generator mode and are driven by rotation ofthe thrust producing elements connected to the individual motors,thereby effecting control of the orientation of the vehicle without theuse of control surfaces.
 8. The aerial vehicle according to claim 1,wherein the number of thrust producing elements is at least eight, thethrust producing elements are grouped into four quadrants with at leasttwo thrust producing elements located in each quadrant, the controlsystem is adapted to reverse the rotation of a first thrust controlelement in a first quadrant, vary the rotation of a second thrustcontrol element in the first quadrant, when all thrust control elementsare not operating in a quadrant opposite the first quadrant, therebyeffecting control of the orientation of the vehicle.
 9. The aerialvehicle according to claim 1, wherein one or more of the thrustproducing elements are adapted for hover and one or more of the thrustproducing elements are adapted for forward flight.
 10. The aerialvehicle according to claim 1, further comprising: a battery energy levelmonitor for determining the energy level in the battery configured totake a first measurement of the voltage in the battery at an initialepoch under a substantially no-load condition, relate the voltagemeasurement to a value of potential energy stored in the battery at theinitial epoch, take a second measurement of voltage in the battery and ameasurement of current flow into or out of the battery at a subsequentepoch, integrate the second measurement of voltage and the current flowmeasurement with respect to time, determine an energy change from theintegration, relate the energy change to the initial energy level tocalculate the energy level of the battery at the subsequent epoch. 11.The aerial vehicle according to claim 1, wherein in horizontal or nearhorizontal flight, the control system is adapted to increase rotationalspeed of some of the thrust producing elements to make a yaw turnwhereby the vehicle turns substantially around the yaw axis but does notturn substantially around the pitch or roll axis.
 12. A method ofoperating an aerial vehicle comprising one or more wings, three or morethrust producing elements mounted in a fixed non-articulatingrelationship to the one or more wings, and a plurality of electricmotors for driving the thrust producing elements, comprising:differentially varying the thrust of the thrust producing elementsthereby altering the orientation of the vehicle.
 13. The methodaccording to claim 12 wherein the number of thrust producing elements isselected from the group consisting of 3, 4, 6, 8, 10 and
 12. 14. Theaerial vehicle according to claim 12, wherein the thrust producingelements are selected from the group consisting of propellers, turbinesand ducted fans.
 15. The method according to claim 12, furthercomprising: differentially varying the amount of rotational energyabsorbed by the individual motors when the individual motors areoperated in a generator mode and are driven by rotation of the thrustproducing elements connected to the individual motors, thereby effectingcontrol of the orientation of the vehicle without the use of controlsurfaces.
 16. The method according to claim 12, wherein the number ofthrust producing elements is at least eight and the thrust producingelements are grouped into four quadrants with at least two thrustproducing elements located in each quadrant, further comprising:reversing the rotation of a first thrust control element in a firstquadrant, varying the rotation of a second thrust control element in thefirst quadrant, when all thrust control elements are not operating in aquadrant opposite the first quadrant, thereby effecting control of theorientation of the vehicle.
 17. The method according to claim 12,wherein one or more of the thrust producing elements are adapted forhover and one or more of the thrust producing elements are adapted forforward flight.
 18. The method according to claim 12 further comprising:providing a battery for providing power to the motors, monitoring theenergy level in the battery comprising: taking a first measurement ofthe voltage in the battery at an initial epoch under a substantiallyno-load condition, relating the voltage measurement to a value ofpotential energy stored in the battery at the initial epoch, taking asecond measurement of voltage in the battery and a measurement ofcurrent flow into or out of the battery at a subsequent epoch,integrating the second measurement of voltage and the current flowmeasurement with respect to time, determining an energy change from theintegration, and relating the energy change to the initial energy levelto calculate the energy level of the battery at the subsequent epoch.19. The method according to claim 12 further comprising increasingrotational speed of some of the thrust producing elements to yaw thevehicle thereby inducing the vehicle to roll resulting in a coordinatedturn.